Pressure-control system



Oct. 30; 1928.

R. D. JOHNSON PRESSURE CONTROL SYSTEM Filed NOV. 28, 1925 P at ente clOct. 30, i I ITED STATES.

PATENT OFFICE.

muons n Jonuson, or New roux, N. .Y.

' PRESSURE-CONTROL SYSTEM.

Application"filed-November 2a, 1925. Serial No. 71,966;

i .This invention relates to the'control of pressures in pi e lines and particularly in lines for powerouses and the like where the variations in the demand causefluctuations in the pressures which, unless controlled, will be attended by dangerous surges.

The object of the invention is to provide means for avoiding both excessive drop and excessive rlse in pressure whatever the variations in the demand may be- A further object of the'invention is to providea control system which will have a very ei-hcient and a smooth action throughout a predetermined normal range of pressure fluctuations,

To this end the system of this invention provides a stand-pipe which may be separate a from the usual surge tank andlocated at a differentpoint in the pipe lineso that the stand-pipe or riser and surge tank instead of beinglimited in cooperation by the nclusionof the stand-pipe within-the surge tank, as in prior practice,.may lJG'COll'lblllGd inany desired manner most advantageous to the parto Fig. 1 but show- 9 carrying the fiowrto the power-house 10,

a valve 11 being sometimes provided to shut off the flow from the pipe 8 when desired.

On the upstream side of the valve 11 is the surge tank 12 having a connection 13 from and to the pipe tion 13 into the tank 12 passes through the Jixed orts 14 and at certain times also throng the auxiliary port 15 normally closed by the spherical check valve 16 vertically,

movable 1n the cage 17. The ports 14 are of such cross sectional area. that the head required to forcewater through them under ,a normal load change isthe. difference or somewhat more than the difference between the elevation of the water in the tank 12 correspondin to the load existingbefore the change an the level in said tank which will exist after the load change and when conditions have become again quiescent. Under a lower the level therein.

.to an increase of pressure n the pipe line 1 a reservoir 7' 8. The flow from the connec-.

the tank through the ports 14:; the valve .16 due to its weight will remain seated so that the water will pass inwardonly through the ports 14. lVhen, however, the decrease in the load is greater than a predetermined 111111- imum as in case for instance of a complete shutdown of the plant, the head required to force the augmented quantity of rejected water through ports 14: will be greater than small decrease of load which forces water into under normal conditions andthe-valve 16 will be elevated from its seat by this higher pressure and will permit'additional Water to pass through the sive pressure on the pipe 11118.

must be drawn from the tank 12the outflow will have to pass through the ports 14: since the valve 6 operatesas-a check valve in this direction. v l

Cooperating with .the surgetank12 there is also provided the stand-pipe or riser 20. Any changes in draft inpenstock 9 willbe I transmitted directly to this riser, so that a decrease of draft will force water into the riser port 15 thus reducing the exces In, case of increased loads where water and raise the level therein while an increase I of draft will draw water-from the riser and This riser thus yields and tends to decrease any excessive pressure and likewise builds up pressure ln'the pipe line gradually upon a decrease of draft in penstockt), and vice versa. In this waytheriser cooperates with the surge tank to modify and lessen the pressure rise or pressure drop as the case may be. 1

The riser 20 is of relatively small cross 7 sectional area and correspondingly small volume and consequently an excessive pressure maintained for any considerable timefwill cause the level in the riser to rise above the top thereof so that there will be an objectionable overflow. To avoid this the riser is car ried up to a suflicient height and the auxiliary port 15 of the main tank-is made sulficiently large to hold the pressure rise within the limits of the height of the riser 20. The opening' of the valve 16 thus reduces greatly the height to which the water will rise in the stand-pipe 20 and permits this stand-pipe to be made of reasonable height Without'danger of overflowing. There is also to be noted that the riser 20 does not subtract its area from that of the tank as would be the case were the riser within the tank.

With the riser 20 thus separate from the surge tank 12 a valve 11 may be placed lietween the tank and the riser thus permitting the riser to act as a vent pipe to prevent cotlapse of the penstock 9 upon closing of the valve 11. The tank 12 also retains all of its Water without making it necessary to empty the'tank 12 each time that the valve 11 is closed. The stu'iaration oi the riser also permits the riser to be oi lighter construction as it does not have to be strong enough to resist the inward pressure of the surge tank Water when, as on sudden increase in load with the riser in the surge tanle the drop in pressure on the pipe line dravvs the low from the inciand thus leaves partly empty within the filled tank 12.

This combination of the riser with the valve connection It; to the surge tank autoinatimilly adjusts itsell to take care of the variable requirements of the plant during operation. The opening of the valve 16 prevents any undue rise in pressure upon decrease in load and the supply of pressure from the riser 20 provents any sudden change of pressure following a demand for more power. As shown in Fig. 3 with the riser 20 within the tank 12 the ports 14; from the connection 13' may be provided with valve means such as the flaps 16 to give a large inflow into the surge tank upon a rise in pressure and. a large outflow from the riser 20 upon a drop in pressure. The advantageof having the ports into the surge tank automatically variable so as to restrict the out-flow is that fixed ports of a maximum full open size would be far too large for proper regulation for ordinary increments of load. The combination of a large opening into the surge tank during a rise of pressure and a free opening from the riser during a drop in pressure, while the discharge from the surge tank is restricted, gives the very best control ell'eet for all pressure changes.

Where as shown in Fig. -1- the penstock itself from the surge tank to the pon'enhouse is unusually long ascompared tothe head on the plant it may be desirable to place the riser 25 (p'iite close to the power-house at the button of the hill leaving the surge tan]; itself atl the upper end of the penstocl; 9' at the top of the hill. With the stand-pipe 30 thus interposed l'ietween the power-house and the pipe line. the penstock 9' as well as conduit 8 will be protected against evcessive pressure variations and the pressure and llow conditions in the line between the stand-pipe and the surge tank will be regulated in addition to the regulation eli'ected in conduit 8.

In some installations it may also he desirable to provide the stand-pipe or riser with a, valve 16' (Fig. l) automatically increasing the ogiiening into the pipe upon excessive pressure rise.

l claim zi. In a pressure. control system the combination with a relatively elevated reservoir, of a pipe line supplied tl1(EIGl' T and having an incline at its end portion, a surge tank con nected to said pipe line adjacent the top of said incline, and a separate unenelosed standpipe oi relatively small cross sectional area connected to said pipe line at a lower point of said incline and extending above the level of the water in said reservoir.

2. In a pressure control systeu'i the comhination with a relatively elevated reservoir, of a pipe line supplied thereby having an incline at its end portion, a surge tank connected to said pipe line adjacent the top of said incline, and a separate unenclosed standpipe of relatively small cross sectional area connected to said pipe line adjacent to the lowermost end of said incline and extending above the level of the water in said reservoir.

RAYMOND D. JOHNSON. 

